Generate PEM pub key directly from DER prv key

Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>
diff --git a/tests/data_files/Makefile b/tests/data_files/Makefile
index 55d6cd2..46aa505 100644
--- a/tests/data_files/Makefile
+++ b/tests/data_files/Makefile
@@ -1019,8 +1019,8 @@
 	$(OPENSSL) pkey -in $< -inform DER -out $@
 all_final += ec_x25519_prv.pem
 
-ec_x25519_pub.pem: ec_x25519_pub.der
-	$(OPENSSL) pkey -in $< -inform DER -out $@ -pubin
+ec_x25519_pub.pem: ec_x25519_prv.der
+	$(OPENSSL) pkey -in $< -inform DER -out $@ -pubout
 all_final += ec_x25519_pub.pem
 
 ec_x448_prv.der:
@@ -1035,8 +1035,8 @@
 	$(OPENSSL) pkey -in $< -inform DER -out $@
 all_final += ec_x448_prv.pem
 
-ec_x448_pub.pem: ec_x448_pub.der
-	$(OPENSSL) pkey -in $< -inform DER -out $@ -pubin
+ec_x448_pub.pem: ec_x448_prv.der
+	$(OPENSSL) pkey -in $< -inform DER -out $@ -pubout
 all_final += ec_x448_pub.pem
 
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